There are a variety of prior art approaches to concentrating and controlling the magnetic field in magnetic read/write heads for recording and reading with respect to magnetic media. Conventional such heads are configured in a horseshoe or U-shaped configuration for the magnetic flux circuit, typically with some enhancement at the gap at the end of the device's arms for the purpose of diverting the magnetic flux outwardly from the gap towards the magnetic medium.
Sometimes the gap flux concentration enhancements take the form of sandwiches of conducting and insulating material to establish eddy currents at the gap to create magnetic forces diverting the flux from the head circuit. Examples of this are shown in U.S. Pat. Nos. 3,072,750 by Barry, 3,246,384 by Vice, 3,508,014 by Mersing and 4,646,184 by Goto et al. Japanese application No. 60-154315 by Ogawa which it is understood was published on Aug. 14, 1984 employs a recording head with the magnetic flux path interrupted at the gap by a superconductor material. It is known that a material in its superconductive state may block passage of magnetic flux therethrough with appropriate thickness, purity and B-field level (the Meissner effect). It may also guide magnetic flux through vortex regions and bend flux lines towards the material surface. Accordingly, the superconductive plug in the Ogawa head gap should cause maximum magnetic flux density outwardly from the gap and in the direction of the medium.
Magnetic fields are used as bearings as in U.S. Pat. No. 3,810,683 by Keever et al. Use of superconductors for supporting bearings is known as in U.S. Pat. No. 3,378,315 issued to NASA wherein a superconductor material is used for a spindle bearing with either permanent magnets or electromagnets providing the supporting magnetic field after the more conventional lubricant has outgassed in the atmospheric void of space. U.S.Pat. No. 3,026,151 by Buchhold also shows superconductor bearings but with the actuator coils likewise formed of superconductor material. Shimuzu et al in the Oct. 1972 Bulletin of the JSME (Vol. 15, No. 88) at pages 1299-1305 shows superconductor wires in coils cooperating with magnetic plungers to support them by levitation.
Use of superconductor elements to form a motor is suggested in U.S. Pat. No. 3,005,117 by Buchhold as well as in the Feb. 4, 1960 issue of Machine Design/Engineering News at pages 14-15. It is also known to use magnetic fields for linear bearings as in U.S. Pat. No. 4,065,188 by Riddler et al which discusses a device using magnetic lubricant at the bearing faces but does not teach how to apply superconductors for such a purpose.
Gilmore in the July 1962 issue of Electronics World (pages 23 et seq) surveyed a variety of the then known cryogenic switches and superconductor devices including magnetic bearings using superconductors, superconductive memory circuits, superconductive power storage devices, frictionless motors, and zero-loss power transmissions. Perhaps Gilmore was somewhat overly optimistic in predicting the speed with which the various superconductor applications would develop. However, contemporary superconductor material discoveries have generated renewed interest in these devices.
Extremely sensitive magnetic field detecting structures are evolving. These devices are sometimes referred to as SQUIDs which is an acronym for Superconducting Quantum Interference Device. One configuration for a SQUID employs two Josephson Junction devices in parallel. Despite the more recent advances in superconductor material, none of the known prior art has effectively harnessed the phenomenon so as to realize the highly efficient and high density magnetic reading and writing as is obtained by the present invention. Further, the incorporation of various superconductor features in a magnetic drive system pursuant to this invention is not suggested in the art including the structure of a superconductor linear actuator useful for magnetic disk applications, optical disk applications, and other information storage systems.